Telephone-exchange system.



B. E. CLEMENT.

ELEPHONE EXCHANGE SYSTEM.

APPLIUATION FILED APB.Z4,1907.

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E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED APB. 24,1907.

1,107, 151 Patented Aug.11,1914.

6 SHBETS-SHEET 3.

E. B. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED APR. 24,1907. 1 ,1 O7, 1 5 1 Patented Aug. 11, 1914 6 SHEETS-SHEET 4.

awwnto'a Wihwoou I c g E B. B. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

nruonron mum APB.24,1901.

1,107,151. Patented Aug. 11, 191 1 6 SHEETSSHEET 5 anwntoz wit" no E. B. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION rum) APB..24,1907.

1,107, 151. Patented Aug. 11,1914

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UNITED s'rA'rEsfPAtrENT OFFICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO FREDERIC]; C. STEVENS, OF ATTICA, NEW YORK.

TELEPHONE-EXdHANGE- SYSTEM.

Specification ef Letters Patent.

Patented Augx'll,- 1914;

Application filed Apr1l24, 1907. Serial No. 370,051.

To all whom it may concern:

Be it known that I, EDWARD E. CLEMENT,

have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a specification, reference being had therein to the accompanying drawing.

My invention relates to telephone exchange systems, and particularly to semiautomatic systems in which automatic 5 switches or their equivalent are employed to effect inter-connection of lines as determined by manual apparatus controlled through the agency of operators.

My invention vision of a number of sets of switching apparatus suflicient for the probable needs of the service, but not necessarily has for its object the proequal to the number of lines. and most desirably less than the number of lines; the provision of operators controlling sets less in number than the number of lines, and the distribution of the load that is to say, the incoming calls, among the sets of switching apparatus, and among the operators, whereby uniform efficiency in service may be attained.

For the sake of simplicity in description I shall specify herein automatic switches of the type known as Strowger selectors and connectors, the construction of such switches being well shown in Letters Patent No. 815,176 and No. 815,321, granted to Keith and Erickson, March 13, 1906. The circuits commonly employed with these switches are well known to those skilled in the art. I shall also specify a type of common battery line circuits and central oflice talking circuits which are considered standard, and generally known as two-wire bridged battery circuits. It is to be understood however that in specifying the apparatus and circuits mentioned they are used as types for purposes of description, and not as limiting the invention.

Stated in terms of the embodiment thus presented. the present invention comprises a number of groups of selector and connector switches less than the number of lines to be served: a number of primary selector switches normally set back to a fixed or Zero and adapted to connect the calling of selector and lines with the said groups connector switches; a number of operators selective keys and impulse transmitting means controlled thereby, with automatic secondary selector switches normally set back at a zero or idle position, and acting to connect the trunks from the primary selector the calls are received, whereby the operators may connect with the calling subscribers, and may actuate the appropriate selector and connector switches to connect the calling and the wanted lines.

By having all the primary and secondary selector switches normally set back to Zero, 1 effect a uniform distribution commencing always with the first trunk or the first position. When a subscriber calls in, current in his line energizes a relay which starts up his primary selector switch, said switch continuing to progress step by step until its wipers rest upon the terminals of an idle trunk, at which time the cut off relay of the line receives current from the switch circuit, the switch stops, and the secondary selector switch is started to connect the trunk to an idle operators circuit. An appropriate sigeach operators circuit, an the operator being thus apprised of a call is able to connect her telephone through her circuit, to the trunk and thence to the calling line, and

and forward to its automatic first selector switch 'to secure connection with the line wanted. Testing and ringing of the Wanted line are automatic.

The specific distinguishing invention claimed in the present case is that each line has a terminal selector switch by which it may be connected in calling to an idle trunk line leading to a first selector vided with a switch starting up from a zero or normally inoperativeposition to select and 'connect with a trunk line upon which a call is landed. This operators switch remains connected to the trunk as long as suflices to send the proper, impulses for settin the switches to complete the connection, after which it returns to Zero and is ready to be started up again by another call, to select the trunk thereof.

My invention is illustrated in the accompanying drawings in which- 1 Figure 1 is a diagram showing a calling 1 subscribers line and a portion of the central naling means such as a lam is provided for feature of the so switches to the operators apparatus when afterward to transmit impulses to. the trunk switch; and each operators circuit is prooflice equipment. Fig. 2 is a similar diagram complementary to Fig. 1, and intended to be placed below the latter, showing another portion of the central oilice circuits. Fig. 3 is a similar diagram also complementar to Fig. 1', intended to be'placed at the rig tof the latter, and showing a selector and connector switch with their circuits, through which the calling line may be connected with any one of a considerable number of other lines' Fig. 4 is a diagram of circuits complementary to Fig. 2, intended to be placed at the right of the latter. Fig. 5 is an end view of an improved rotary selector switch. Fig. 6 is a section on the line XX of Fig. 5. Fig. 7 is a similar view with the bank contacts removed, of a modification of the switch shown in Fig. 5. Fig. 8 is a diagram showing connections between operators sets whereby the calls are properly distributed and more than one operators selector switch is prevented from being set into operation by a single call.

Referring to Fig. 1, A is a subscribers station connected to the central ofiice by the line wires 1 and 2, which are normally connected through the contacts of a cut-off rclay N to the line relay M and to ground, respectively, the line relay being connected to the main battery through the wire 3. Line extensions 4 and 5 pass from the cutoff relay to the wipers of a step by step selector switch S, this switch being what is called a single motion or rotary switch, having a spindle s journaled so that it can turn upon its axis, and provided with a ratchet 'wheel by which it may be turned. This ratchet wheel is engaged by a stop or detent pawlz' controlled y the electromagnet 8', and a stepping or working pawl controlled by the electromagnet 8 The circuit of the electromagnet s is controlled by the line relay M through its armature m, for which purpose the front contact 7 of the relay is connected by -a wire 8 and interrupter I with the ma et a while theiarmature m is connected with the battery wire 3. This interrupter is continuously operating and may consist, as shown, of a rotative cylinder having alternate conducting and insulating portions, one conductor being connected with the conducting portion and another with a pen bearing upon the cylinder, so that as the cylinder rotates the conductors will be alternately connected together and disconnected as the pen successively bears upon the conducting and insulating portions. The cylinder is continuously driven by any suitable means. With such an arrangement it is onl necessary to maintain the circuit closed w on the successive energizationsand deenergizations of the magnet and vibrations of its armature will continue indefinitely. In the present case, as the magnet s vibrates its armature, it also turns the spindle s by means of its pawl and the ratchet on the spindle, any retrograde motion of the spindle being prevented by the fixed stop pawl controlled by the magnet s. The-spindle is provided with a return spring preferably a coiled spring, which has a constant tendency to turn the spindle back against the pawl of the magnet s and which when this pawl is released by the energization of its magnet, will actually turn back the spindle into its, normal, zero or inoperative position. The mechanical construction suitable for a switch S as described will be set forth hereinafter. The line relay M also partially controls the circuit of the release magnet 8'. For this purpose the armature m is connected to the main battery wire 3 through the branch 6. The circuit of this release magnet is normally open at the springs a and b, which are worked by a device on the spindle 8, being open when the spindle is back in zero position and closed as soon as it leaves that position. The release circuit is further controlled by the cut-off relay N, through a back contact 11 connected to the wire 12 and cotiperating with the armature M, which is grounded through the Wire 12. In order that the re lay magnet 8 may be energized, therefore, it is necessary for the switch to be set away from its normal position, and for the relays M and N both to be deenergized. This condition'is only brought about when a connection has been made and the subscribers have hung up their receivers.

The switch S has in its bank trunk contacts s, which cooperate with the switch wipers s, and e test or signaling contacts 8 which cooperate with the wipers 8 The multiples of these bank contacts which as shown in Fig. 1 are of course supposedtobe distributed in diflerent switches, the Wires from each trunk being multiplied to as many lines switches as may be desired. A convenient arrangement contemplates 100 multiples, there being ten trunks, and each trunk being represented by a multiple contact in each line switch of 100 lines. Each line thus has access to ten trunks, and each line switch need only have ten sets of contacts s, s in its banks. Instead of using the rotary switch, I may make the single motion of the switch vertical, the contacts 8*, s then being arranged in vertical rows and the wipers 8 8" being stepped up along the rows by means of the magnets 8 When the release magnet 8 works, the spindle s will then be restored by gravity, and the springs a and b will be placed beneath the spindle so that its weight will open them.

The contacts 8', s are the terminals of the trunk circuits, and one of these trunk ci'r'. cuits is shown in Figs. 1 and 3, leading to a selector switch S This trunk is marked 13, 14, 15 and 16, and its extensions in Fig. 3

idle trunk, and then closes or operating selector switch S,

are marked 17, 18. A pair of condensers C' is interposed in the circuit or the purpose of separating the same into two portions for battery currents, these currents being fed both ways in the operation of the system. Across the answering end of the trunk, 1314, are bridged the two relays R and R, with the main battery B between them. The tip relay R is grounded, and the sleeve relay R is connected to the live side of battery, which is the usual arrangement in circuits of this type. The tip relay R responds to the act of the calling subscriber and controls the clearing out of the automatic apparatus; the sleeve relay becomes energized when the switch S picks out an the circuits of the magnets R and R, which are res ectively the stepping magnet of the secon ary and a looking relay serving also as a cut-off relay for shifting the control after the operators circuit is connected. The functions of those several relays will best appear from the statements of their operation hereafter. The relays R and R are combined cut-oii and repeating relays. The relayR when energized over the operators wire 20 pulls up its armature, breaks apart the wires 15 and 17, and connects the latter to the wire 21 leading to the battery wire 3, so as to send an impulse of current through the trunk wire 17. Similarly, when the relay R is energized over the operators wire 19, it pulls up its armature to break apart the wires 16 and 18, and connects the latter to the wire 22 and thence to the battery wire 3, thus sending an impulse of current forward over the trunk wire 18. When both of these relays R and R are simultane ously energized, they connect the operators wires 19 and 20 to the wires 15, 16, respectively, so that the operator may connect her telephone to said wires 15 and 16 and communicate with the calling subscriber.

.The multiple test contacts 8 are normally connected by a wire 23 to the contact 24 and thence through the contact .25 and conductor 25' to the battery wire 3, whereby the contacts s are connected directly to the battery B, so the testcondition of an idle trunk is that these contacts have their potential raised to the full voltage of the main battery. When the relay R becomes energized, however, which, of course, occurs when the trunk is busy, the contacts 2 1 and 25 are separated by armature r and the battery connection made through the resistance 27 whereby resistance 27 is interposed bet-ween the battery and the contacts 8 This condition continues while the circuits are in use, and suffices to give a busy test, since the cutoti" relay N of such line is connected through a wire 28 to the wiper s of the line switch S. This wiper passes over the contacts 8 when the switch is operating and the cutoff relays are so wound and adjusted that they will pull up on direct battery connection but will not pull u on the connection through a resistance 2 Their arrangement is such, however, that any 1' lay which has already been pulled up wi old up on one-half full the current and therefore on the fiow through the resistance 27, so that when the wiper s of a line switch asses over the terminal s of trunks whic are already busy, the relay N of the calling or testing line will not pull up but the relays of the lines already in use will continue to hold up.

The trunk wires 17 and 18 extend as shown in Fig. 3 to the side-switch arms 8* and s of the selector switch S. This switch isof the Strowger type referred to in the beginning of my specification, having a main spindle arranged for both vertical and rotary movements, this spindle being placed at the axis of a set of contacts arranged in ten rows of ten each. Carried on the spindle are talking-circuit wipers s, which coi' peratc with the bank contacts 8 and a test wiper s which cooperates with the multiple test contacts a. The switch spindle is stepped up to bring its wipers opposite the desired row of contacts by means of the soralled vertical magnet 1; controlled through a relay V; and the rotary movement of the switch is brought about by means of a vibrator magnet 42' which makes and breaks its own circuit as it vibrates and is controlled by the relay T when the side switch arm 8 is in its second or intermediate position.

It is unnecessary to give here anyextended description of the circuits and apparatus of Fig. 3, all of these being old and well known to those skilled in the art. 7

Q is a release relay of the switch and q is the release magnet governed thereby. The other parts of the apparatus as well as the circuit connections will suiiiciently, appear from the statement of operation hereinafter.

S designates a connector switch which is designed to cooperate with a selector switch S It has a similar spindle carrying wipers 7 s and s. The test is made on the tip or upper side of the line. This switch also contains line contacts in its banks arranged in rows of ten each. The spindle is stepped up to bring the wipers s oppositethe desired row by means of a so-called vertical magnet 71 and is rotated step by step by means of a .so-called rotary magnet 4), which in this case is not a ,vibrator but responds to distinctive current impulses, since the desired line is identified with a single pair of contacts only, and therefore the row of contacts must be selected and the pair of-contacts in the row afterward picked out nect with an idle trunk line in any desired group. In the operation of the selector necessary, and in such case conductor 43 through Thus, the main battery switch, therefore, the spindle is stepped up by means of definite and distinctive impulses to the row of contacts 8 and 8 representing the desired group (which may be either thousands or hundreds and in this case hundreds), and after that, when the side switch has taken one step the rotary magnet 0 takes control of the switch and steps the spindle around continuously as long as the 'wi er 8 finds ground on the contacts 8 W cn this ground fails (the busy contacts being grounded and the idle one open) it means that an idle contact has been reached, and thereupon the side switch is moved a third step to cut oil the rotary magnet and stop the wipers upon this ungrounded or idle cont-act.

The connector circuitcontains a pair of condensers C for the reason that the for ward impulses which work the switch must not be confused by the battery current supplied to the called subscriber. We may assume that the switches of Fig. 3 are both in the same building with the, apparatus of Figs. 1 and 2 although this is not at all the battery B shown separate in the two figures is of course the same battery. For the purpose of supplying talking current to the called subscriber, I connect this battery to the sleeve conductor 44, of the connector switch, through a relay R and I ground the tip the relay R which is the samegas connecting it back to battery. is also bridged across the conductors 43 and 44 through the relays R and R which as in the case of the relays R and R in Fig. 1 are wound to approximately 100 ohms each, but present igh impedance to voice currents. R is the ringing relay, which controls the application of the ringing generator G to thecalled line and is itself controlled on the one hand by the relay R and on the other by the commutator K, which may be common to all the ringing relays of the exchange. The

' circuit of theringing relay is indicated at 45, 46, 47, 48, 49 and 50, being terminated at the ground through the commutator on one .end and at the battery wire 3 on the other end. This circuit is controlled by the relay R and this relay does not become enere 'gized until the side-switch arms s 8 s and s have made their last step so that the conductors 43 and 44 are completed from the condensers G to the wipers a and a. Before this last step of the side-switch is taken, the wi' ers a and s have been placed upon t e terminals of the wanted line, and the release relay Q, plied to the tip side of the line pose of testing.

has been ap for the pur- The circuit of this relay is as follows: 51, 52, 53, 54, 55, 8 56 to tip wiper 8 If the line wanted is busy, there is a grdund on the tipside, either by way of a relay R or by way'of a relay R, depending on whether the line originated the call upon which it is engaged, or was called by some other party. In either case the test or release relay Q, will receive current; but if there is no ground because the line wanted is idle, then the test relay remains unafi'ected, the talking circuit is completed, and the sleeve relay R becomes energized by ourrent passing to the wiper s and thence through the multiple contact a (see Fig.'

l) and the 'cut-ofi' relay N to. ground. The culgcfl? relay there-upon pulls upand the ringing relay circuit is at the same time'completed, so that the commutator K takes control thereof. It will be observed that this circuit 46-47, passes through a back contact on the relay R", which 1S controlled on one side by a pair of contacts under the foot of the spindle switch 8 and on the other side by front contacts of the tip relay R which does not pull up until the called subscriber answers. When this occurs, the relay R becomes energized, locks itself by way of wires 50 and 57, and opens the ringing relay circuit 46, 47, 48, etc. The relay R is controlled by the subscriber in the in tervals of ringing, .for it will be observed that the commutator K has segments where by it closes the ringing circuit at intervals only. While this circuit is open. therefore, and the relay R deenergized in consequence, the subscriberhas control of the relay R. In order that the relay R 'may remain energized through the ringing intervals, I provide a special batteryconnection, as shown.

The arrangement of switches shown in Fig.

'3 is suflicient for exchanges up to 1000 line capacity; but in order to provide for-more than 1000 lines. another set of selector switches is required, interposed between the trunk ends of Fig. ,1 and the switch S of 'Fig. 3. The capacity of the exchange can be increased indefinitely without altering those circuits by adding these sets or groups of switches in the well understood manner. The selector switches all have the same circuit as that shown at S and therefore I have considered it unnecessary to multiply illustration by showing more than one. It is within the power and skill of every person having a fair knowledge of the automatic 'art to add as many sets of selectors as may be desired. Regardless of the number of switches, the method of operation, which has an important bearing upon the operators equipment, is .to send'the selecting or working impulses over the trunk wire 17,

rotary w ire.

' opened by whi h isconuuonly called the vertical wire, and to send the controlling impulses over the trunk wire in which is commonly called the These so-called rotary inipulses serve to work the side switch magnets 'l and T, and thereby to shift the side switches so as to bring into play successively the vertical and rotary magnets, the test relay, etc.

heterring now to the lower part of F ig. 1 and to Fig. 2, there is therein shown an operators equipment and its selector switch for, connecting a calling trunk therewith.

The selector switch is marked S and is similar in its construction to the primary selector switch b. It has a spindle s and wiperss 8 and s. It is rotated by means of a pawl and ratchet actuated by a rotary vibrator magnet R and it is held in any position to which it is turned by a stop pawl controlled by the release magnet s. The circuit of the rotary vibrator magnet is closed through an interrupter l, similar to l, by the sleeve relay R of the trunk and the relay R, which is controlled by the relay R, which receives current when an idle operators set has been connected with the trunk. The release magnet s has its circuit controlled by the relay R being connected in parallel with the signal light L between the point .r and round. The relay R is initially controllec by the relay R which has its circuit made through the switch wiper 8 after that wiper has stopped upon the contact a which is connected through contacts of relays R and R of the connected trunk to ground. The wipers s and 8" of the operators selector switch will then-rest upon the contacts 8 and 8*, respectively, which are respectively connected to the operators wires 19 and 20. the switch being stopped in this position by reason of the energization of the relay R whereby the circuit of the rotary step by step magnet R is broken. It will now be apparent that when a subscribers line has been connecte with a trunk that the sleeve relay R of that trunk will become energized and a switch S of an idle cperators set will start up from zero and the wipers s 8 and s' will sweep over the bank contacts 8 s and s, respectively, until these wipers reach the contacts connected with the trunk which has been connected up with the calllug subscriber,- when the switch S is stepped. After the operator has performed her functions and theconnection through thetrunk wires 1'? and 118 is completed to the wanted subscribcrs line, the release magnet s restores the switch S to its zero or inoperative position.

In order to prevent more than one operators selector switch from being started by a call upon a trunk, interlockingmeans is employed, which means is shown in Fig. 8,

taken in conjunction with Fig. 1, portions of the apparatus, not necessary to an explanation of the feature under consideration being omitted from Fig. 8.

' Referring to Fig. 8, a back contact of the armature on each of the relays R, 1R, 2R, etc., of the trunks. is connected with a conimon conductor 80. The armatures referred to are connected, respectively, to ground through armatures and front contacts of the relays R, 1R, 2R etc. while a relay R, 1R, or 2R of a trunk is de'energized and the relay R, 1B or 2R of the same trunk is energized, which is the condition when a trunk has been connected to a subscribers line and before an operators equipment has been connected thereto, the conductor 80 is connected with ground. One terminal of each of the stepping magnets R IR and 2R etc. is connected with the conductor 80 and it will therefore be apparent that when any trunk is connected with a calling subscribers line all of the stepping magnets of the switches S, 18', 28, etc., corresponding to the operators equipment will be grounded. The selection of which one of the operators selector switches is to be operated depends upon the connections of those terminals of the stepping magnets which are not grounded as above described. The ungrounded terminal of each of the stepping magnets is connected through an interrupter I, II or 21, as the case may be, to the back contact of an armature of a relay R, 1B or 2R of its ref spective operators of the armatures referred to is connected to a front contact of its corresponding arma ture in an adjacent equipment so that when one of these armatures is moved to break the connection of the stepping magnet of its own equipment it forms a connection for the corresponding armature of another equipment. It will be noted, however, that one of these armatures is an exce tion to the general statement just made or, being at one end of the series of operators equipments it is connected directly to battery.

Let it be assumed that all of the operators equipments are idle and that any one of the trunks has been connected witha subscribers line. The conductor 80 will then be grounded as before indicated and, it will be seen that the circuit of the stepping magnet of the selector switch S only will have its ungrounded terminal connected with battery through its interrupter, the battery connections of the stepping magnets 1R 2R etc.', being broken at the front cont-acts ofthe armatures of the relays R 1R, 2R ,-etc., respectively. The battery connection of the stepping magnet B being thus made through the armature of the relay R and its back contact, this magnet will be. inter l mittently energized and the switch l wil It will thus appear that equipment, while each he stepped into position to connect the trunk with its operators equipment. When this connection has been formed, the relay R, IE, or 2B according to which trunk is connected, will be energized and, attracting its armatures will break the ground connection to the wire 80 whereu on the circuit of the magnet R will be bro en and the switch S will stop. The connection of the operators equipment with the trunk also results in the energizing of the relay R which thereupon attracts its armatures and breaks the battery connection of the stepping magnet R between the armature of that relay and its back contact as before referred to. Any subsequent forming of a ground connection for the wire 80 by a calling trunk will not, therefore, form a circuit for the stepping magnet R while the operators equipment to which it corresponds is in use and therefore the relay R energized.

The operators set corresponding to the switch S being in use and the armatures of the relay B being attracted, thereby disabling the stepping magnet R it is to be noted that the armature at which the circuit of the stepping magnet just referred to is broken, has now come against its front contacts and thereby establlshes a battery connection from one terminal of the stepping magnet 1R of the selector switch 1S through the interrupter 1I, conductor 81 and armature of its relay IR and its back contact and thence through conductors 82 and 83 through an armature and front contact of the relay R to battery. Any grounding, therefore, of the conductor 80, which is occasioned by the connection with a subscribers line of a trunk, results in the intermittent energizing of the stepping magnet 1B and the stepping of the selector switch 1S into position to connect the trunk with the operators equipment corresponding to the switch. In a similar manner to that described in connection with the operators equipment corresponding to the switch S, the connecting of the equipment corresponding to the switch 18 will result in the opening of the battery connection of the stepping magnet of the last mentioned switch and the closing of such connection for the stepping magnet 2B of the next operators equipment which will be set into operation by the next calling trunk. In a similar manner the connection of the operators equipment corresponding to the switch 2S will result in the forming of a battery connection for the stepping magnet of the succeeding equipment and so on to the limit of the apparatus.

From the foregoing it will be apparent that, as the battery connection of only one operators stepping magnet is made at a time, it will be impossible for more than one of the operators selector switches to be started at a time or by a sin 1e call. It will further be observed that w ere the simultaneous use of several operators equipments is required, the equipments so used will be successively selected from one side of the apparatus to its limit at the other. With the a paratus thus far described for securing t e successive connection of operators equipments, if the stepping magnet of one equipment has its connection made through another previously selected equipment and the equipment last mentioned were to have performed its function and have been cleared out, the circuit of the stepping magnet of the former would be broken, and, the selector switch controlled by that magnet being in process of being step ed into connecting position, the switc would be stopped in whatever position it might happen to be at the time of the breaking of the circuit of its stepping magnet and confusion might result. To avoid such a contingency, means is provided for preventing the breaking of the battery connection of the stepping magnet of a switch after such connecing operation has been completed, regardless of whether equipments through which the circuit of the particular magnet is made are cleared or not. The specific means shown for accomplishing this end consists in the provision at each operator selector switch, except that one in which the circuit of the stepping magnet is made directly to battery of contacts a and b. In other words these contacts are rovided at every selector switch which has 1ts battery connection made through another equipment.

Each pair of the contacts referred to is adapted to be opened when its switch is in its initial position but to be closed in all other positions of the switch. The mechanical construction of a switch having these contacts is shown in Figs. 5 and 6. One of each pair of contacts is connected with battery while the other is connected with the conductors as 82 and 83 leading to another equipment and through which the battery connection of the stepping magnet as IR is made. It will now be apparent from an examination of Fig. 8 that, the contacts as a and b of any switch being open 'at the initial position of the switch, that the initial battery connection of its stepping magnet as 1R (except of course that equipment which has direct battery connection) is made through another equipment or equipments but that after such connection has been made and a selector switch has been started, circuit of the stepping magnet of that switch will be maintained until the stepping operation is completed, regardless of whether the equipment or equipments, through which the initial connection was made, is or are cleared out or not.

90 tion has once been made, until the connect- In the lower part of Fig. 2, I have shown the apparatus which appears in front of one operator, consisting of a set of buttons only.

i bove these in the figure I have shown a.

set of wheels or sections of a drum with the cooperating springs, the motor and the common commutator of the central office sending machine. This machine furnishes'the impulses by which the selector and. connector switches are worked in order to select the line wanted, and the number of impulses sent as well as their arrangement is determined by means of the operators keys or buttons. Thes'e keys are in three sets, K, K and K ,each set having ten buttons controlling. contact springs k, is. The springs k of all the buttons in each set are joined to a common wire, and the ends of these three common wires are connected together at the point 7c", from which point the conductor leads as shown in Figs. 2 and 1 to the multiple contact a in the bank of the switch S. The spring 10 of each key is connected to a pen of the a propriate disk or zone on the sending mac ine drum. When any particular button is depressed therefore it connects its individual wire to the common wire 70. The individual wires of the keys K are marked respectively 71, 7 2, 73, 74, 75, 76, 77, 78, 79, 80. Similarly the individual. wires from the keys K are marked 81, 82, s3, s4, 85, so, 87, 88, 89, 90, and the individual wires of the keys K are marked 91, 92, 93, 94, 95, 96, 97, 98, 99, 100. In practice these keys are arranged with the strips perpendicular to the front of the desk, the units strip on the right hand side, the tens strip next in order to the left. and so on. In the present drawings however for convenience, the keys are arranged in horizontal rows, with the units row at the top. The sending machine comprises the main commutator I), having a brush (Z connected to the main bat tery, and riding over itssegmcnts so as to produce regularly recurring makes and breaks in a continuous series. In practice this commutator is made with a pair of spring contacts and teeth or cams are formed on the body of the commutator to work these springs up and down, but for convenience of illustration I have shown the brush resting directly on the periphery of the disk. With such a construction in actual practice and considering that this commutator will carry a large number of switching impulses simultaneously, I prefer to make the brushd of carbon. This is a detail, however, which may be varied at will and does not affect the invention.

The commutator D is graphically shown as carried on a shaft (13 whicih through all of the number- "whee s forming both the mechanical and electrical connection therewith. The mechanical connection is not shown in the drawing but the electrinumber wheels each of which makes and extends cal connection is indicated by a wire marked d. The number wheels are shown at d, (1 d, d, d 41, (Z (P, d al each having a tooth or raised segment of a suitable length to cover the space of the number of teeth on the commutator D equal to the number of impulses the particular wheelv is to transmit. Thus the first wheel d has a single tooth d, approximately equal in length to only one tooth on the main commutator. The second wheel has a single tooth (1 approximately equal in length to two teeth on the commutator and so on. In other words, instead of using a set of S0 breaks through a number of teeth, I have shown all the makes and breaks on the main commutator, and in order to send any desired number of impulses, I select a wheel which will maintain connection with the com.- mutator while the desired number of impulses are being produced and are then cut off therefrom. Another peculiarity of the arrangement is that the makes and breaks on the number wheels (2, d d etc., are made during the passage of gaps on the main commutator when there is zero potential, and hence there will be no sparking at the number wheel contacts. In order to do this I may either subdivide the commutator surface evenly and equally into alternate conducting and insulating segments and then make each number wheel tooth slightly longer than that of the particular tooth to which it corresponds, or I may make the conducting portions on the commutator smaller than the insulating portions and make the number wheels teeth of lengths equal to the exact multiple of a unit snbdivision.

It will be observed that there are four sets of pens on the number wheels. These will accommodate four sets of keys K, K etc. If a greater number of digits appear in the numbers to be transmitted, the wheels must be rovided with additional sets of springs. The set K has its individual wires connected to the first set of springs cl, the set K has its individual wires connected to the set of springs H, and the keys K are similarly connected to the spring pens rl. The general direction of rotai ion of the commutator and the various wheels connected to it is clockwise as shown by the arrows in Fig. 2, and the teeth on the wheels come into contact with the spring pens in the order (1, d, (Z Thus the number set up on the set of buttons K is transmitted over the wire 70 first, then follows the number set up on the buttons K and so on. Thus for the 1 5 number 468 the operator would depress the fourth button in the set K. The sixth button in the set K arid the eighth button in the set K". By tracing the circuits it will be found that when the controlling circuit are closed, which occurs at the beginning of a rotation when the wheels are all in the position shown in Fig. 2, current will pass from the main battery to the commutator D, thence to the wheel d, thence by wire 94 to the fourth key in the set K and thence to the wire 7 0 and so on to the wire 20 and the relay R in Fig. 1 which repeats the im pulses over trunk wire 17 to the switches. As the wheels continue! their rotation this circuit will be broken after four impulses have been transmitted, and then a new circuit will be formed carrying current from the battery through the commutator to the sixth wheel at, and thence from the second spring a! on that wheel through the wire 86 to the key which is closed, thence the wire 70 and thence again to the relay R which repeats to the switches. After these impulses have been sent by this route, this circuit will be broken and a new circuit will be formed from the main battery through v to the third pen thereon, 0Z thence to the eighth key in the set K which has been closed, thence to wire 70 and to the relay R as before. The closures between the wheels and successive sets of springs are arranged to be separated by intervals, during which no current at all flows to the wire 70. These intervals are necessary in order to permit the switching circuits to be arranged so as to reduce the proper results in response to the successive sets of working impulses. In other words, having shown therein a set of Strowger switches, I must provide not only the vertical or working impulses in groups, but I must also provide the interposed or rotary impulses between said groups. This is accomplished by means of the wheel d", which has four teeth in quadrature, and all adapted to make contact with the single pen d, which is connected by the wire 170 to the multiple contacts 8 in the banks of the various selector switches S, and thence through the wire 19 to the relay R, which repeats the rotary impulses over the trunk wire 18 to the switches. The wheel d" is insulated from the shaft (17, and is grounded through the wire 101, this being neces sary because the relay It" is connected on the other side to the battery wire 3. In other words, the repeating relay R, which is controlled by the number wheels, is the grounded relay and so the number wheels take battery impulses from the commutator: but the relay R is on battery,- henre the rotary wheel d" uses the ground to work the relay. The. reason I make one of these relays grounded and the other connected to battery is in order to pull them both up simultaneously when the operator has her telephone set bridged across the wire and 170 in Fig. 2.

Hitherto the selector switches referred to as S and S have been referred to only as regards the electric circuits and contacts with which they are associated and in this connection the diagrammatic illustrations in Fig. 1 have been suflicient. Mechanical features of a switch adapted to perform the functions of the switch S S of Fig. 1 are shown in Figs. 5 and 6. This switch comprises a frame a on which is mounted a bank I) of contacts consisting of ten rows of contacts of three contacts each. The contacts of different rows are adapted to be successively engaged by Wipers c, d, e, which are fixed upon the rotatable shaft f, the contacts c, d, e, being respectively insulated from each other. A spring 9 interposed between the shaft f and a stationary part as the frame, tends to rotate the shaft f to one limit of its movement, when the contact arm carried by the shaft will not rest upon any of the bank contacts as shown in Fig. 5.

Fixed upon the shaft f is a ratchet h.

mature m is normally held retracted by a spring 0 while the nose of the pawl k is thrown outwardly by means of a spring p, extending between the armature m and the tail of the pawl k. The outward movement of the nose of the pawl 70 is limited and it is guided in its movement by a stationary pin 9 In order that the holding pawl i may be disengaged from the ratchet h so that the contacts upon the shaft f may be returned to their normal position under the influence of the spring 5/, a magnet a known as the release magnet is provided. The armature s of the release magnet is retracted by means of a spring t, this armature being limited in its outward movement by a nut u in a screwthreaded engagement with the screw 3 mounted upon the frame of a magnet and extending through the armature s. Obviously the nut to is capable of adjustment 'along the screw 1 to permit greater or less movement of the armature s Carried by the armature a of the release magnet is a resilient arm w which carries a ratchet tooth 0/ adapted to engage with the lower end of the holding pawl 2'. An arm y mounted upon the armature n of the stepping magnet overlaps one end of the arm w and is adapted to draw down one end of that arm so that the lower end of the pawl i will clear the tooth :2 when the armature of the stepping magnet is attracted.

The operation of the apparatus is as follows: Assuming the parts to be in position as shown, as impulses are supplied to the stepping magnet its armature will be attracted a number of times equal to the number of the impulses and at each attraction the pawl is will be thrown forward into engagement with the ratchet wheel and will move that wheel forward a distance depending upon the adjustment of the various parts, which are so adjusted that at the first impulse the wipers upon the shaft f-will be moved into engagement with the first row of 7 bank contacts and will be moved to a succeeding row upon each impulse thereafter. The shaft and wipers which it carries will be prevented from retrograde movement by the holding pawl which is forced into engagement with the ratchet h by its spring. A desired row of the bank contacts having been reached in the manner described and the object for which the connection was established having been accomplished, it becomes necessary to return the wipers to their zero ornormal position in readiness for another operation as just described. This restoration is effected by denergizing the release magnet s, it having been previously energized, when its armature will be retracted, drawing the tail of the holding pawl i with it, and the nose of that pawl will be disengaged from the ratchet h and the wiping contacts will be returned to their initial position. In the next selective operation of the switch, however, it is necessary that the holding pawl i shall engage with the ratchet h to hold the contacts in any position to which they may be stepped. It, therefore, becomes necessary to release the pawl z from the arm prior to the succeeding stepping operation. This is accomplished by means of the arm y which upon the first energization of the stepping magnet and the attraction of its armature, will draw down with it the free end of the resilient arm w thereby freeing the pawl i whereupon its nose will be thrown against the ratchet h by the spring I. The contacts a and b operated by the projection a are useful in some applications but are not used in the apparatus herein illustrated and so will not be further referred to.

It will be noted in. regard to the switch just described that the release of the wipers occurs upon the deenergization of the release magnet, the holding pawl being in position to engage the ratchet and restrain the wipers so long as the release magnet remains energized after having once been excited. It

may be, however, as in the case of switch S, that .it will be of service for the release of the wiper contacts to occur upon energization of the release magnet and for the holding pawl to be disengaged fromthe ratchet even though the release magnet may be (leenergized. A structure adapted for operation in this manner but in other respects like the switch just described is shown in Fig. 7. On reference to this figure it will be seen that the holding pawl i is pivoted at e and its nose is normally held in engagement with the ratchet by the spring (1. The tail of this holding pawl is adapted to be engaged by armature s of the release magnet 8'. When the release magnet is energized, its armature is attracted and the holding pawl i is moved against the spring (1 so that it clears the ratchet, when the wiper contacts are {free to return to their initial position. When the armature a is attracted, it carries with it the. resilient arm w, the tooth a," of which latches behind the stationary detent z. The holding pawl is thus locked away from the ratchet until, at the first impulse in the stepping magnet s at the ;beginning of 7 another selective operation the arm y is drawn downwardly and unlocks "the arm '10 from the stationary detent, whereupon the holding pawl comes into enga ement with the ratchet. The operation of t is switch is in all respects similar to that of the switch in Figs. 5 and 6 except as to the releasing means above indicated.

The operation of the system can be best set forth by tracing the connections and noting the operations of the various arts of the apparatus which are involved rom the time a call is initiated at a subscribers station until the conversation has terminated and the apparatus has been restored to its normal condition. Let it beas'sumed that a subscriber at a station a s-A desires to converse. He removes the receiver from its hook when the latter rises andestablishes a connection, through his transmitter and receiver, between the lines 1 and 2. A circuit is then established from the free terminal of the battery B through the wire E), line relay M, armature n, line 1, subscribers set, line 2 and armature n to ground. The relay M, being thus energized, attracts its 9.1- mature m a circuit then being established from the free side of battery B through conductors 3 and 6, armature m, interrupter I, conductor 8 and stepping magnet 8 to ground. The magnet 8 15 then intermittently energized, as its c1rcu1t is made and broken by the interrupter, which results in the. reciprocation of the stepping pawl (see Fig. 7) and the stepping forward of the wipers of the switch S from one row of bank contacts to the next at each energization. In the initial poslt-lon of the switch, the circuit of the magnet s is broken at the contacts a, b and the switch does not move from this position until the relay M is energized and then although the contacts a and'b' are closed, the armature m is attracted and the connection between that armature and wire 10 is broken. The

l release magnet beingthus deenergized, the

holding partl a is in: engagementfwith the 7 ratchet wheel andholds thewipersin'hny position to which they maybe stepped.

The wipers are stepped from one row of lnajnk colitactsto the neXt in' the nmnncr' de- 1 scribed until-thejwipers Wands rest upon f the eontacts as 's-' ands of an idle trunk,

whcnthe circuit of thecut-ofhrlay N is 1 made front the ground through the"relay, wire 28, wiper 3?, contacts, Wire 23' and contacts 2& and 25,120 conductor 3', connected tothe free side of'the battery B, {there bethe relay N.

g ilBgligible resistance the circuit of When a connecting" trn'nk 1;; in cperation or busy, the relays R and R are energized when the circuit from the contact 2 1 through the" branch connection of negligible resistance will be opened. connection, ho'w ever, may he traced from the contact 24 through theresistance .27 to; the condnctor As'has been before pointed out, thls re 'sistance isfof such magnitude that it will permit'suflicient current to flow, so that the .relayN will hold its armatures after they have been once attracted, but the' cnr- L're'nt'ivill be insufficient to cause the relay N 60 initially attra'ct" its armature. It will now appear as the Wiperss and 8- pass over the conthcts "-of busy connected thinks, that the 'arrnatures' of the relay N will not attracted ind the stepping of the switch will continue nntil the test Wiper-t" comes. againstthetest contact .9 of an idleoon- 35 necting itrl nk "whemthe"hircnit of 'l'ow resistance will. be formed 'throughthe relay N of the calling suhscriber whereupon the ar; matures offthe relay Will be attracted.- The afinatn res 'n='and' 'n""of the relayN 'be 40 ing 'thlis'removed "from their back contacts,

the ciroiiit'ofthe line relay M will be broken and its armature m wili'fall back and come into contact with the hack contact '9, while the circuit "thronghth'e wire 8 of the stepl ping magnet will be brol'ze'n hyth'e armaturefm and the stepping of the vill.

- cease. l The contacting of the armature mend the =ture referred to and its contacfl 111' The holding pawl of the switch, therefore, is in, :engagement'with the ratchet'upon the switch shaft so that the Wipers are ,I'nainteinedin: the position to Whichthey have beenst'epped.

Theswi'tch S hzivingbeen'stepped into position, as described, circuit may be traced from the free side of the battery 13 through moms:

the relay Rto sleeve side l l' of thejtrunk thence throngh one of..them1i ltiple contacts the: snbsc'riberfs" line armature n. of the lay N, conductor, 2 of the subscribers line I the snbscribers instrument, conductor ;1 of thesuhscr'ihers line,'a rn at ire n of the re-' my N, 'eXtehsionf i of snbsc'ribers line, the other' wiper 8 6f the switch S, the other ninlt'iple contzict s, ithe tip side 13 of the tr'nnk'zf'nd' the'relay R to ground. Acircl it' hh'ynig thnsibeen completed, the-armathresfof the. relays R and R are attracted i The" attraction of thear natures 27' and 3r n emte'to close. the. circuit 'of the stepping relhy Rf and the test(contact s of the operators selector, swxtchfwith ground. i The circuit of the relay It may be traced from "the free side of the battery B through the conductor conductor 68, interrupter lay R conductor 80, gu ineturel -f of the re- R"; f ndi 't lf i a ma r 3 an 2 hduotor '86 tojgronnd Fron the test oontect of the switch S, circuit may be traced through the conductor, 101,. armature r, cond1 1ctor lO 2 and armature 22jto ground. The

nrmatnres 21' and 31" are,connected bya ture Zrfiisettincted, is connected through thht armature v a nd n conductor 10'? and condnct0 r 3 'With' the free side of the battery.

,W'hen the n atures Zr end 3r are; not at.

'8", one of, the wipers .s-", .'the extension i of Y condnct or "1015 "with the vc onductor106, which, i when the reley lt isienerg ized and its arma trncted, the relay B ,being deenerg'ized,

these arrnetu res Will fbe respectively in connection, with the conductors 108 and, 1:09 which are, respectively,connected tothe tip ,nnd slecv'esides' lii and l6 of the trunk, connected so that ivhen the relay Rf is decnergized both sides 15 and 16 of the trunk Will be connected with battery.

Themagnet R being intermittentl energized will reciprocate its,pa Wl-, see igs. 5

and Send descriptions thereof stepping the switchforward. Wh en the Wiper s rests upon the contact 8 circuit, may be traced from the ground through armature 21*, comdnctor 102, armature 1- c0nductor 101, comtact s, wiper s conductor 49', armature 1r, conductor 50 and magnet R? to battery," In coming against its front contacts the armature 21", establishes connection for the stepping magnet. of the. next .opera-tors selector switch as hereinbefore described. The attraction of the armature 1' against its front contact/closes the circuit from the ground through relay R conductor 52, cond uctor 20,' contacts, wiper s conductor 53, armature "r conductor 54", makebefore-break contacts 55 and 56', relay R conductor, 57', and armature r to. battery. The relays 'R 'and R sre thus energized and their armetnr'es attracted. As the ar t.

nurture"? comes against its front contact 56, the contacts 55' and 56' separated thus breaking the circuit just traced, the ground connection of the relay R being owever maintained through the armature r and contact 56'. It will be seen that the relay R has been momentarily energized and that its armature 1' has been momentarily brought against its front contact thereby momentarily closing the circuit of the relay R from the ground through armature 31a, conductor 85, relay 11*, conductor 106, conductor 59 and armature r to battery. The relay R is then energized and attracts its armatures, the armature 21" coming against its front contact and locking battery connection on the relay B so that its circuit is maintained after the relay R has been deiinergized. The attraction of the armatures 1" and 10* breaks the connections of the trunk with the operators stepping magnet and its connections with the multiple contacts 8 of the operators selector switches, the ground connection for the relay R, formerly made through the contact a, being maintained by the armature 11' which has been attracted against its front contact and which is connected to ground. The armature 21' has also been attracted against its front con- 7 tact whereby circuit is established from battery through conductor 68, armature 2r and the front contact thereof to point at whence a portion of the current passes by light L to ground and the other portion passes through release magnet 8 to ground. The release mechanism is thus set to engage the holding pawl of the switch S (see Fig. 5) and the operator is notified of a call by the lighting of this lamp. Connection may now be traced from battery through relay R, conductor 19, contact 8 and wiper s to conductor 17 Connection may also be traced from ground through relay R conductor 52, conductor 20, contact 535, wiper 8. conductor 53' and armature 1' to conductor 70.

Referring now to Fig. 2, it will be seen that the conductors 17 and 7 are adapted to .be connected by means of the pressure of a button 0 with the conductors 127 and 128, which lead to an operators set of usual construction and hence not shown. It will be seen that upon the depression of the button 0, that a circuit will be completed from the battery wire at one side of the relay R through that relay the operators set, and the relay R to ground. Talking current will thus be supplied to the operators set and also the relays R and R will become energized, whereupon they will attract their respective armatures 11" and 1' and one of the operators conductors 20 will be connected with the trunk conductor 16 while the other operators conductor 19 will be connected with the other trunk conductor 15. It will now be apparent that the operators set and the calling subscribers instrument will be so connected that conversationmay be had.

The operators set and subscribers instrument having been placed in conversational communication as described, the operator inquires of the subscriber the number of the wanted subscribefs station. Let it be assumed that this number is 468. The operator depresses the fourth key of the set K, the sixth key of the set K and the eighth key of the set K In this manner the conductors 94, 86, and 78 are connected with the common point is, these conductors bein respectively connected with the pen 0! o the drum section (1, the pen (2 of the section d and the pen al of the drum section (i The commutator D is driven b a motor M and, the motor supposed in te particular apparatus shown to be normally at rest, it becomes necessary to start the motor and commutator. To accomplish this, the operator depresses the button 0' and thereby connects the conductor 130, which is connected to one terminal of battery to the conductor 131 and thence through the conductor 132 to the relay R and to ground. The relay B" being thus energized its armatures r and 11" are attracted when circuit will be closed from the battery wire 109 through the last mentioned armature, conductor 133 and relay R to ground. The relay R being thus energized will attract its armatures 7' and 11-. The circuit of the relay R to battery through the armature r is thus broken but this connection is made through the armature r" of the relay R whereby the control of the relay R is transferred from the relay R to the relay R Circuit may be traced also from the motor conductor 134 through the armature 11' and a suitable generator and a motor starter as indicated which may be-of any well known type to the other motor conductor 135. The motor will thereupon start up and place the commutator in operation. There is also set in operation a starting disk which is of conducting material with the exception of an insulating segment 136 upon which the pen 137 normally rests. After the motor and with it the commutator, starting disk, rotary disk and drum sections are set in operation by the depression of the key 0, as described the pen 137 will ride off the insulating segment and maintain the circuit initially closed, by the depression of the button 0. This circuit being closed the motor, commutator and. disks will continue to revolve until the pen 137 again rests upon the insulating segment 136, when the circuit willbe broken and the apparatus will stop. During this rotation, first the pen (I corresponding to disk d will be engaged by the contact segmentupon the said disk, which is of such a length as to maintain the conductor 94, the contacts of the fourth .of the switch S,

button of the row K-to the point It" thence throughthe conductor 70 to the contact 8 conductor and relay R v to ground. Ateach of the four impulses, the relay R will be energized and attract its armature 2r against its back contact c0n nected with the battery B. At each impulse, therefore, the tip side 17 of the trunk will be'c'cnnected with battery and the impulses will be repeated over this side of the trunk to ciperate'the automatic selector and con- Hector switches as before descr1bed;thenext operation consists of the sending of a'rotary impulse,occasioned by the coming in'contact projections upon the disk 03". This action causes the"closure of a circuit from the ground through a conductorlOl, disk d", pen (Z conductor 170, contact 8 of the switch S, conductor 19, and the'relay R to the hattery Wire 3. Each projection on the dish c is 01% such len th' as to transmitbut one impulse and this impulse passing through the relay R through the circuit just traced, the relay last mentioned attracts its armature in against its back contact thereby crmnecting the sleeve side 18' of the trunk monuntarily with the battery wire 3,

when a rotary impulse is transmitted over the sleeve side for working the side switches of the automatic selector and connector switches as before indicated; after the sending of therotary impulse as described, the conductin segment of the disk'd comes in contact with its pen d when six impulses are sent over the conductor 86 to the point It", whence circuit is the same as before through the relay R and 'six vertical impulses are transmitted over the tip side 17 of the trunk. The

the trunk before and eight vertical impulses are then transmitted over the tip side by reason of the contact upon the disk a?" pen tl ,*connectceiver breaks the circuit with the pen d of one of the conducting .tures of this re disk at" then sends an other rotary impulse overthe sleev'e side of' of the connecting'operation breaks; the' circuit as before traced through the relayjR which thereupon releases its armature'there by breaking the circuit of the relay R which in turn releases its armature '21"? thereby breakingthe circuit of the release magnets when (see Fig. 5). the holdihg pawl i will have its nose removed gagement with the ratchet uponthe switch shaft and the switch will return to its, zero position,thus leaving the operators'set 'idle in readiness to operation'for another connecting trunk and its subscribers instrument. The circuit of the relay R will be broken at the armature 1r whereupon the motor circuit will be broken at the armature 11'.

Connections between having been established as described. the hangingup of the calling subscribers reat the hook through his instrument thereby breaking the circuit 1 of the relays R and R whereupon their armatures are released and the circuit of the cutout relajy' N is broken. The armaay being released, theline wires 1 and 2 of the calling subscriber are disconnected from their, extensions t and 5. The armature n being released, connects one of the contacts a, b with ground through the conductor 12' and the switch'S being out of its initial position, the contacts a and b are in' contact. The circuit of the release magnet can then bev traced from the battery wire 3 through the conductor 6, armature m, conductor 10, magnet 8', contacts it, b, conductor 12 mam-ma ture n to ground. The release'magnet will thus be energized and the holding pawl will be removed from' engagement. with the ratchet upon the switch shaft whereupon the switch will return to its initial position (see Fig. 7). The magnet R being deenergiz ed, its armature 31' will break the circuit of the magnet R The armature QrflhoweVer, is

arranged to act sluggishly when released so that the connection of the conductor 105 with the battery wire 3 is maintained after the armatures 2r" and 31- have come against their back contacts. This being the case, it will be seen that the two sides 15 and 16 of the trunk are simultaneously connected with battery, this results in the simultaneous energization of the relays V and V the circuit of the relay V being traceable from the trunk conductor 41 through the relay V and conductor to ground while "the circuit of the relay V is traceable from the trunk conductor 42 through relay V to ground. Relays V and V having thus been energized and their armatures at tracted, circuit may be traced from battery wire 52,. release relay Q, conductor 53, conperform the connecting the two subscribers ductor 64, bank contact 8, Wiper 8 release relay Q, conductor 38, side switch arm .9 and conductor 39 to ground. The release relays Q, and Q being thus energized will attract their armatures when the eircu1tof the release magnets g and g of the switches S and S respectively, will be closed whereupon those switches Wlll. be released and will return to their normal positions.

I do not claim broadly herein the combination of primary selector switches associated with the lines and secondary selector switches associated with operators sets, each of the primaries and each of the secondaries containin fixed terminals of connective trunks. Such a combination broadly is disclosed in my prior application Serial No. 327,096, filed July 20, 1906. Neither do I claim herein broadly a semiautomatic system in which incoming calls are distributed among idle connective links, and through secondary mechanism are distributed among the idle operators positions, the operators controlling selective switches for completing connection between sul scribers. Such subject matter is disclosed and claimed in my prior copending applications Serial No. 323,096, filed June 23, 1906; Serial No. 327,096, filed July 20, 1906; Serial No. 369,201, filed April 20, 1907; Serial No. 383,874, filed July 15, 1907; and 383,875, filed July 15, 1907. Such subject matter is also disclosed in Letters Patent granted to me July 14, 1914, No. 1,103,898.

The claims in this case are directed particularly to that type of system in which all of the primary and secondary switches have a normal or zero resting position from which they are started into operation and to which they are restored at the end of re spective operations. v

Having thus described my invention,what I claim and desire to secure by Letters Patcut is:

1. In a telephone exchange system, a number of subscribers lines, a primary selector switch for each subscriber's line. a number of t unks less than the number of subscribers lines, each of said trunks having at one end multiple contacts in said switches, a first selector switchat the other end of each trunk, an operators circuit and apparatus including a telephone set and a sending device, and an automatic switch associated with the operators circuit and containing terminals of a number of said trunks, all of the switches specified being normally in a. zero or inoperative position and adapted to be started up to test and connect with bank terminals in their numerical order, substantially as described.

2. In a telephone exchange system, a number of subscribers lines, a primary selector switch for each subscribers line, a number of trunks less than the number of subscribers lines, each of said trunks having at one end multiple contacts in said primary selector switches, a first selector switch at the other end of each of said trunks, an operators circuit and apparatus including a telephone set and a sending device, an automatic switch associated with the o erators circuit and containing terminals 0 a number of said trunks, and restoring means for said switches, substantially as described.

3. In a telephone exchange system, a number of subscribers lines, a primary selector switch for each subscribers line, a number of trunks less than the number of subscribers lines, each of said trunks having at one end multiple contacts in said primary selector switches, a first selector switch at the other end of each trunk, an operators circuit and apparatus including a telephone set and a sendlng device,an automatic switch associated with the operators circuit and containing terminals of a number of said trunks, driving means for the primary selector switches started by the calling subs'cribers, and driving means for the operators switches controlled by the primary selector trunks, substantially as described.

4. In a telephone exchange system,anumber of subscribers lines, a primary selector switch for each subscribers' line, a number of trunks less than the number of subscribers lines, each of said trunks having at one end multiple contacts in said primary selector switches, a first selector switch at the other end of each trunk, an operators circuit and apparatus including a telephone set and a sending device, an automatic switch associated with the operators circuit and containing terminals of a number of said trunks, driving means and release or restoring means for said primary selector switches, said driving and release or restoring means being controlled by the calling subscribers and driving means for the operators switches controlled in the use of the primary selector trunks, substantially as described.

In a telephone exchange system,anumber of subscribers lines, a primary selector switch for each subscriber's line, a number of trunks less than the number of subscribers lines, each of said trunks having at one end multiple contacts in said primary selector switches, a first selector switch at the other end of each of said trunks, an operalors circuit and apparatus including a telephone set and a sending device, an automaiio switch associated with the operators circuit and containing terminals of a number of said trunks, driving means and release or restoring means for the said primary selector switches, said driving means and said rclmsc or restorino means being controlled by the calling subscribers, driving means and release or restoring means for the operators or secondary switches, said driving means and release or restoring means for the operators switches being controlled in the use of the primary selector trunks, substantially as described. 6; In a telephone exchange system, a number of subscribers lines, a primary selector switch for each subscribers line, a number of trunks less thanthe number of subscribers lines, each of said trunks having at one end multiple contacts in said primary selector switches, a first selector switch at the other end of each of said trunks, an operators circuit and apparatus including a telephone set and a sendin device, an automatic switch associated with the 0 erators circuit and containin terminals 0 a number ofsaid trunks, riving means and rele IIB or restoring means for the said primary selector switches, said driving means and said restoring or release means being controlled by the calling subscribers, driving means and release or restoring means for the said operators switch, said driving means and stud release or restoring means for the operators switch being controlled in the use of the trunks and driving means for the forward or calling selector switches controlled by the operator, substantially as described.

7. In a telephone exchange system, a number of subscribers lines, a rimary selector switch for each subscribers ine, a number of trunks less than the number of subscribers lines, each of said trunks having at one end multi le contacts in said rimary selector switc es, a first selector switch at the other end of each of said trunks, an operators circuit and apparatus including a telephone set and a sendlng device, an automatic switch associated with the operators circuit and containing terminals of a number of said trunks, driving means and release or restorin means for the said primary selector switches, said driving means and said release or restoring means being controlled by the calling subscribers, driving means and release or restoring means for the said operators switches the said driving and release or restoring means for the operators switches being controlled in the use of thetrunks, driving means for the forward or calling selector switches controlled by the operator,

and release or restoring means for the said calling selector switches controlled over the lines connected, substantially as described.

8. In a telephone exchange system, a plu- V rality of subscribers lines, a primary selector switch for each line, connecting links less in number than the number of lines having multipled contacts in said primary selector switches, an automatic impulse sending device, an operatorsmanual means for controlling said impulse sending device, an automatic switch associated with said operators controlling means for connecting said sending device with one of said link circuits automatic switches arran ed to be actuated over said link circuits 311E means for restoring all of said switches to their normal posltions.

9. In a telephone exchange system, subscribers lines, a primary selector switch for each of said lines, link circuits less in number than the number of lines, operators sendin devices, a selector switch associated wit each sendin device and arranged to select one of said llllkS, automatic means for effect,-

a talking connection through the imv 1n pfises from said sending machine and means for restoring all of said switches to their normal inactive positions.

10. In a telephone exchange system, a plu rality of subscribers lines, primary selector switches associated with the lines, a lurality of connective link circuits having xed terminals in said switches, an operators equipment including a telephone, and an automatic switch associated individually therewith containing terminals of branches from the link circuits, whereby the operators outfit may be associated with any link for purposes of connection, together with means to restore said operators switch to normal or inactive position when each line connection has been established.

1]. In a telephone exchange system, a plurality of subscribers lines, primary selector switches associated with the lines, a plurality of connective link circuits having fixed terminals in said switches, an operators equipment including a telephone, and an automatic switch associated individually therewith containing terminals of branches from the link circuits, whereby the operators outfit may be associated with any link for purposes of connection, together with automatic means to restore said operators switch to normal or inactive position when each line connection has been established.

In testimony whereof I aifix my signature in presence of two witnesses.

EDWARD E. CLEMENT.

Witnesses:

E. EDMONSTON, Jr., Jos. L. VRIGHT.

c091 of this patent may be obtained for five centseaeh, by addressing the Commissioner of Patents.

Washington, D. 0. 

